SAN FRANCISCO (CBS/AP) — A California water district that is the country’s largest says it has reached a deal with the federal government in a decades-long dispute over thousands of acres of contaminated land.

The San Francisco Chronicle on Sunday reported the agreement involving the Central Valley’s Westlands Water District, which covers 1,000 square miles of some of the country’s most lucrative farmland. The 600 farms in the water district produce $1 billion in crops annually.

The agreement concerns a bungled, Congress-approved 1960s irrigation project that contaminated at least 100,000 acres of the Central Valley with selenium, salt and boron. In the 1980s, the buildup of minerals caused deaths and birth defects in thousands of fish and birds.

The new agreement, contained in a short public document crafted by the U.S. Bureau of Reclamation and the Westlands Water District, says the Westlands Water District would handle the drainage problem that led to the mineral buildup. Taxpayers would be relieved of the estimated $2.7 billion cost of removing contaminated water.

The federal government, in turn, would forgive $342 million in federal debt owed by the water district.

Members of Congress still would have to approve the proposed agreement.